The present invention relates generally to semiconductor fabrication and, more particularly, to a hollow core spindle and a spin, rinse, and dry module including the hollow core spindle.
As the semiconductor industry moves to larger, e.g., 300 mm, wafers and to smaller, e.g., 0.18 xcexcm and smaller, feature sizes, it is becoming increasingly more important to control wafer contamination on the backside, i.e., the bottom side, of wafers during wafer preparation operations. In one conventional wafer preparation operation, a wafer is spin rinsed in a spin, rinse, and dry (SRD) module. During this spin rinsing operation, deionized (DI) water is sprayed onto the top side and the backside of a wafer as the wafer is spun at high speed. One problem with this spin rinsing operation is that recirculating air from above the wafer often causes particle recontamination on the backside of the wafer.
FIG. 1 is a simplified schematic diagram 10 illustrating the airflow around a wafer in a conventional bowl, which forms part of an SRD module. As shown therein, wafer 12 is disposed in bowl 14. For ease of illustration, the spindle, which spins the wafer, and the spindle fingers, which support the wafer above the spindle, have been omitted from FIG. 1. As wafer 12 spins in bowl 14, the spinning action of the wafer transfers energy to the air flowing to the top side of the wafer. This transferred energy causes the airflow above the top side of wafer 12 to become turbulent and creates recirculating air, i.e., eddies, as indicated by the arrows in FIG. 1. The amount of energy transferred to the air flowing to the top side of wafer 12 depends on the diameter and the rotational speed of the wafer. In general, the greater the amount of energy transferred to the air, the higher the eddies extend above the top side and the farther the eddies extend below the backside of wafer 12. The presence of eddies below wafer 12 is undesirable because particles or DI water droplets removed from the wafer can circulate in the eddies and be redeposited on the backside of the wafer, thereby causing recontamination.
In view of the foregoing, there is a need for a device for controlling the airflow on a backside of a wafer during spin processing to minimize the recontamination caused by particles and DI water droplets circulating in eddies below the wafer.
Broadly speaking, the present invention fills this need by providing a spindle having a hollow core through which fluids can be delivered to the backside of a semiconductor wafer. In combination with a wafer backing plate, the hollow core spindle enables the airflow on the backside of the wafer to be controlled. The present invention also provides a spin, rinse, and dry module including the hollow core spindle.
In accordance with one aspect of the present invention, a spindle is provided. The spindle includes a hollow central shaft having an upper end and a lower end. The hollow central shaft defines a channel for transmitting fluid therethrough. A wafer backing plate is disposed at the upper end of the hollow central shaft.
In one embodiment, the hollow central shaft is an actuator shaft and a hollow spindle shaft is concentrically disposed around the actuator shaft. In one embodiment, the hollow spindle shaft has a pair of high speed bearings and a housing mounted thereon. In this embodiment, the housing encloses the pair of high speed bearings. In one embodiment, the size of each of the high speed bearings is the same.
In one embodiment, a mounting plate is disposed at an upper end of the hollow spindle shaft, and a spin chuck is mounted on the mounting plate. In one embodiment, the actuator shaft is configured to move vertically to actuate the spin chuck for supporting the wafer as well as to rotate. In one embodiment, the wafer backing plate is mounted on the spin chuck. In one embodiment, the wafer backing plate is mounted on the spin chuck with at least three spring-loaded pistons. In one embodiment, the wafer backing plate has a shape that substantially corresponds with the shape of the wafer.
In accordance with another aspect of the present invention, a spin, rinse, and dry (SRD) module is provided. The SRD module includes a bowl and a hollow core spindle for rotating a semiconductor wafer that extends into the bowl. The hollow core spindle has a channel defined therein for transmitting a fluid to the backside of the wafer and a wafer backing plate disposed at an upper end thereof. In one embodiment, the wafer backing plate is configured to block particles from contacting the backside of the wafer.
In one embodiment, the SRD module includes an internal air supply tube disposed within the channel and an air source in flow communication with the internal air supply tube. In one embodiment, the air source is an ultra low penetrating air (ULPA) filter unit. In one embodiment, the distance the wafer backing plate is disposed below the wafer is in a range from about 80 thousandths of an inch to about 275 thousandths of an inch.
The hollow core spindle of the present invention allows fluids, e.g., air and chemistries, to be delivered through the spindle directly to the backside of a semiconductor wafer disposed above the spindle for spin processing. This is beneficial in and of itself because it avoids the atomization problems that occur when chemistries are sprayed onto the backside of the wafer through rotating spindle components. In combination with the wafer backing plate of the present invention, the hollow core spindle is further beneficial because it enables the airflow on the backside of the wafer to be controlled so that contaminated air does not recirculate into the volume defined by the wafer and the wafer backing plate. Moreover, the wafer backing plate of the present invention advantageously reduces particle recontamination by preventing particles from contacting the backside of the wafer.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.